This invention relates to microwave monolithic integrated circuit (MMIC) radio frequency modules, and more particularly, this invention relates to a millimeter wave (MMW) transceiver module using microwave monolithic integrated circuit (MMIC) chip packages.
Microwave monolithic integrated circuits (MMIC) used in radio frequency (RF) modules have traditionally been built in low to medium volume. The key elements that prevented this technology from attaining high volume production, similar to surface mount technology components, is the difficulty in working with fragile MMIC chips and the tight tolerances required when manufacturing such components.
A millimeter wave (MMW) module is typically made up of dozens of MMIC chips, substrates and discrete components mounted with epoxy or solder to a Coefficient of Thermal Expansion (CTE) matched carrier or similar machined housing. The radio frequency components are typically connected to other components and terminal pads via wire or ribbon bonds. Tuning of the radio frequency modules after assembly is almost always required.
Although many chip manufacturers are now offering individual MMIC chips in a surface mount package, an entire receiver, transmitter or local oscillator (LO) multiplier have not been provided in a single chip package to enable production of a MMW module with fewer surface mounted components. In addition, the unavailability of a wide array of surface mount MMIC chips has caused designers to shy away from their use because of the requirement to mix bare die with surface mount chips.
Another reason why single transmitter, receiver or LO multiplier MMIC chip packages have not been available is because these types of devices require some level of filtering of unwanted signals. A receiver requires image rejection, a transmitter requires local oscillator (LO) signal rejection, and a frequency multiplier requires filtering of a fundamental frequency. Prior art filters used in conjunction with such devices were traditionally made from thin film material, and were too large to mount into a small chip package. Some prior art devices, however, have been fabricated as a MMW receiver chip using image reject mixers, such as shown in FIG. 1.
FIG. 1 illustrates a receiver chip 20, having a low noise amplifier 22 that receives the radio frequency signal, a capacitor 24 connected to ground, and DC signal coming in and operative at drain voltage Vd. An image reject mixer 26 receives the local oscillator (LO) signal and is operative with in-phase (I) and quadrature (Q) channels. An external L-band hybrid combiner 28 receives the intermediate frequency, as illustrated. These receiver chips have not seen wide commercial acceptance because of their limited image reject performances and the requirement to use an external I/Q hybrid combiner 28 to obtain a single IF output. A hybrid combiner at L-band also is very large in comparison to the high frequency chips used in such devices.
The present invention advantageously overcomes the prior art drawbacks and provides a millimeter wave (MMW) transceiver module and method of fabricating same by using a low cost microwave monolithic integrated circuit (MMIC) transceiver chip set that is surface mounted on a circuit board, such as a printed circuit board of the type known to those skilled in the art. The MMIC chips are provided as miniature sized surface mount packages and use multilayer, low temperature, co-fired ceramic thick film technology, such as formed from layers of low temperature transfer tape using fabrication techniques known to those skilled in the art.
In accordance with one aspect of the present invention, the millimeter wave (MMW) transceiver module of the present invention includes a circuit board and a microwave monolithic integrated circuit (MMIC) transceiver chip set that is surface mounted on the circuit board. The MMIC transceiver chip set includes a receiver MMIC chip package, a transmitter MMIC chip package, and a local oscillator (LO) multiplier MMIC chip package. Each chip package is surface mounted on the circuit board. These components are operatively connected to each other through appropriate connections via the circuit board for millimeter wave transceiver operation. Each MMIC chip package includes a base and a multilayer substrate board formed from layers of low temperature transfer tape and received on the base. The multilayer substrate board has at least three layers and carries RF signals, DC signals, grounding and embedded passive components, including resistors and capacitors. MMIC chips are received on the multilayer substrate.
In one aspect of the present invention, a filter is formed on the multilayer substrate board and operatively connected to the at least one MMIC chip. The filter is formed by vertically stacked resonators in the multilayer substrate board. In one aspect of the present invention, the filter includes a plurality of coupled line millimeter wavelength resonators formed as stripline or microstrip and positioned on a filter surface defined on the multilayer substrate board. The filter includes radio frequency contacts and conductive vias extending through the multilayer substrate board. The filter could also include a plurality of isolation vias extending through the multilayer substrate board.
In yet another aspect of the present invention, the base can be formed as an alumina plate that is metal plated. Heat sink vias could be formed within the base. The multilayer substrate board also includes a substrate on which the low temperature transfer tape layers are mounted. Each layer of low temperature transfer tape could be about three mil thick, but the range in dimensions could be higher or lower as designed and fabricated by one skilled in the art. A top layer of the multilayer substrate board has chip cut-outs for receiving MMIC chips therein. A plurality of interconnects and interconnect vias are positioned within the low temperature transfer tape layers forming the substrate board.
In another aspect of the present invention, the receiver MMIC chip package includes a low noise amplifier, a mixer and an image rejection filter. The transmitter MMIC chip package includes a power amplifier, mixer and a local oscillator signal filter. The local oscillator multiplier MMIC chip package includes an x-band mixer, amplifier and a filter for filtering a fundamental frequency.
A method is also disclosed for forming the millimeter wave (MMW) transceiver module of the present invention.